gmon/mcount.c

   1 /*-
   2  * Copyright (c) 1983, 1992, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 4. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 #if !defined(lint) && !defined(KERNEL) && defined(LIBC_SCCS)
  31 static char sccsid[] = "@(#)mcount.c    8.1 (Berkeley) 6/4/93";
  32 #endif
  33
  34 #include <unistd.h>
  35 #include <sys/param.h>
  36 #include <sys/gmon.h>
  37
  38 /* This file provides the machine-dependent definitions of the _MCOUNT_DECL
  39    and MCOUNT macros.  */
  40 #include <machine-gmon.h>
  41
  42 #include <atomic.h>
  43
  44 #include <not-cancel.h>
  45 #include <unistd.h>
  46 #define ERR(s) __write_nocancel (STDERR_FILENO, s, sizeof (s) - 1)
  47
  48 /*
  49  * mcount is called on entry to each function compiled with the profiling
  50  * switch set.  _mcount(), which is declared in a machine-dependent way
  51  * with _MCOUNT_DECL, does the actual work and is either inlined into a
  52  * C routine or called by an assembly stub.  In any case, this magic is
  53  * taken care of by the MCOUNT definition in <machine/profile.h>.
  54  *
  55  * _mcount updates data structures that represent traversals of the
  56  * program's call graph edges.  frompc and selfpc are the return
  57  * address and function address that represents the given call graph edge.
  58  *
  59  * Note: the original BSD code used the same variable (frompcindex) for
  60  * both frompcindex and frompc.  Any reasonable, modern compiler will
  61  * perform this optimization.
  62  */
  63 _MCOUNT_DECL(frompc, selfpc)    /* _mcount; may be static, inline, etc */
  64 {
  65         ARCINDEX *frompcindex;
  66         struct tostruct *top, *prevtop;
  67         struct gmonparam *p;
  68         ARCINDEX toindex;
  69         int i;
  70
  71         p = &_gmonparam;
  72         /*
  73          * check that we are profiling
  74          * and that we aren't recursively invoked.
  75          */
  76         if (atomic_compare_and_exchange_bool_acq (&p->state, GMON_PROF_BUSY,
  77                                                   GMON_PROF_ON))
  78           return;
  79
  80         /*
  81          * check that frompcindex is a reasonable pc value.
  82          * for example: signal catchers get called from the stack,
  83          *              not from text space.  too bad.
  84          */
  85         frompc -= p->lowpc;
  86         if (frompc > p->textsize)
  87                 goto done;
  88
  89         /* The following test used to be
  90                 if (p->log_hashfraction >= 0)
  91            But we can simplify this if we assume the profiling data
  92            is always initialized by the functions in gmon.c.  But
  93            then it is possible to avoid a runtime check and use the
  94            same `if' as in gmon.c.  So keep these tests in sync.  */
  95         if ((HASHFRACTION & (HASHFRACTION - 1)) == 0) {
  96           /* avoid integer divide if possible: */
  97             i = frompc >> p->log_hashfraction;
  98         } else {
  99             i = frompc / (p->hashfraction * sizeof(*p->froms));
 100         }
 101         frompcindex = &p->froms[i];
 102         toindex = *frompcindex;
 103         if (toindex == 0) {
 104                 /*
 105                  *      first time traversing this arc
 106                  */
 107                 toindex = ++p->tos[0].link;
 108                 if (toindex >= p->tolimit)
 109                         /* halt further profiling */
 110                         goto overflow;
 111
 112                 *frompcindex = toindex;
 113                 top = &p->tos[toindex];
 114                 top->selfpc = selfpc;
 115                 top->count = 1;
 116                 top->link = 0;
 117                 goto done;
 118         }
 119         top = &p->tos[toindex];
 120         if (top->selfpc == selfpc) {
 121                 /*
 122                  * arc at front of chain; usual case.
 123                  */
 124                 top->count++;
 125                 goto done;
 126         }
 127         /*
 128          * have to go looking down chain for it.
 129          * top points to what we are looking at,
 130          * prevtop points to previous top.
 131          * we know it is not at the head of the chain.
 132          */
 133         for (; /* goto done */; ) {
 134                 if (top->link == 0) {
 135                         /*
 136                          * top is end of the chain and none of the chain
 137                          * had top->selfpc == selfpc.
 138                          * so we allocate a new tostruct
 139                          * and link it to the head of the chain.
 140                          */
 141                         toindex = ++p->tos[0].link;
 142                         if (toindex >= p->tolimit)
 143                                 goto overflow;
 144
 145                         top = &p->tos[toindex];
 146                         top->selfpc = selfpc;
 147                         top->count = 1;
 148                         top->link = *frompcindex;
 149                         *frompcindex = toindex;
 150                         goto done;
 151                 }
 152                 /*
 153                  * otherwise, check the next arc on the chain.
 154                  */
 155                 prevtop = top;
 156                 top = &p->tos[top->link];
 157                 if (top->selfpc == selfpc) {
 158                         /*
 159                          * there it is.
 160                          * increment its count
 161                          * move it to the head of the chain.
 162                          */
 163                         top->count++;
 164                         toindex = prevtop->link;
 165                         prevtop->link = top->link;
 166                         top->link = *frompcindex;
 167                         *frompcindex = toindex;
 168                         goto done;
 169                 }
 170
 171         }
 172 done:
 173         p->state = GMON_PROF_ON;
 174         return;
 175 overflow:
 176         p->state = GMON_PROF_ERROR;
 177         ERR("mcount: call graph buffer size limit exceeded, gmon.out will not be generated\n");
 178         return;
 179 }
 180
 181 /*
 182  * Actual definition of mcount function.  Defined in <machine/profile.h>,
 183  * which is included by <sys/gmon.h>.
 184  */
 185 MCOUNT